Introduction to Safety

Frank Balzer

Alsion, March 2014 International Norms and Standards for Laser Safety

• to ensure a safe use of machinery and to protect operators against hazards

• EN 60825 (IEC 825): „Safety of Laser Products“ • main international standard for laser safety • describes the effect of laser on the eye/skin • defines thresholds • definition of safety classes • labeling, engineering specifications, safety precautions, maximum permissible exposure (MPE) • and LEDs

• ANSI Z136 series, EN 207/208: Laser Safety Eyewear

http://www.lucidos.co.uk/lasersafety/lsstandards.htm http://en.wikipedia.org/wiki/File:Laser_goggles_en207.jpg

27.05.2014 11:39 27.05.2014 11:39 Management Responsibility for Laser Safety

Some Laser Safety Officers (LSO) duties: • safety program • classification • hazard evaluation, control measures, protective equipment, signs and labels … • equipment • audits, surveys, inspections • approval of class 3B or class 4 laser for operation

Management has the fundamental responsibility to ensure the safe use of lasers owned and/or operated in facilities under its control; therefore, it is the employer that establishes and maintains adequate policies and programs for the control of laser hazards, and these policies and programs are generally delegated down to the appointed laser safety officer (LSO). The laser safety policy needs to be integrated into the organization’s overall safety plan or procedure manual and needs to be reviewed at a specific interval, no less frequently than once every two years. The LSO must have authority and support of management for a successful program. K. Barat, Laser Safety in the Lab

27.05.2014 11:39 Are Lasers Dangerous?

Laser Type % victim % Nd:YAG 29,7 technicians 21,3 Argon 20,5 scientists 17,6

CO2 12,8 patients 12,9 dye 9,9 plant workers 10,7 HeNe 7,0 medical personnel 9,2 others 20,1 students 8,4 spectators 4,8 others 15,1

source: Rockwell Laser Incident Database, www.rli.com 7974 registered accidents between 1964 and 2010, (395 accidents until 1999)

27.05.2014 11:39 Laser Hazards

• primary sites of damage: eye, skin

27.05.2014 11:39 Danger of Laser Radiation

• powerful laser radiation is dangerous, mainly for eyes and skin • examples of accidents:

of eye:

burns of skin: Ar ion laser

27.05.2014 11:39 Examples for from the Laser Accident Database

Case: 5326 , Year: 1977 , Country: USA "Relatively weak" Nd:YAG laser was being aligned when portion of beam from system optics went into eye. He heard a popping sound. Interocular bleeding and particles observed. Some pain followed by condition of shock. Partial blindness resulted.

27.05.2014 11:39 More Examples from the Laser Accident Database

Case: 7961, Year: 2010, Country: Switzerland 15-year-old Swiss boy purchased a handheld laser online as a "toy". He ended up damaging his … while trying to create a "laser show." His vision was so reduced he could not even read a news paper. He had a hemorrhage in his left eye and scarring in his right. Vision in his left eye improved from 40% to 80% after treatment.

Case: 6658, Year: 2005, Country: USA Subject standing on the second floor of an apartment building pointed a laser device at deputies and continued to track them during their investigation. One of the deputies became concerned they were being targeted by a laser-sighted weapon asked the man to show his hand. The man refused that request and made a sudden movement which the deputy believe was of imminent hazard. The deputy then fired a shotgun at the man, which struck him in the chest killing him. No gun or laser was found near the body, but an inspection of the apartment revealed the presence of three handguns and three laser devices, including a gun-mounted device.

Case: 5643, Year: 1988, Country: United Kingdom Student accidentally viewed stray reflection from argon laser used on an optical bench. A senior researcher received peripheral retinal damage. Shrouding was inadequate to limit reflections.

27.05.2014 11:39 Laser Basics

• „ Amplification by the Stimulated Emission of Radiation“

• properties • monochromatic • coherent • small divergence

• modes of operation • continuous wave (cw) • pulsed

• laser medium • gas • dye • solid • semiconductor http://www.nmm.ac.uk/rog/2009/01/

27.05.2014 11:39 Electromagnetic Radiation Spectrum

• lasers: UV – IR, 180 nm – 1000 µm  laser radiation can be partly or completely invisible  can pretend false safety

27.05.2014 11:39 Exposure Types

1. intrabeam exposure 2. specular reflection 3.

reflection plane surface

reflection curved surface

diffuse reflection much less dangerous

27.05.2014 11:39 Laser Types

• gas (Helium-Neon Laser) • dye • solid state (Nd:YAG, Ti:Sapphire) • diode

27.05.2014 11:39 Laser Types in the Optics Lab

Ar ion laser Excimer laser

Diode laser KGWO4 laser

27.05.2014 11:39 Laser Types in the Optics Lab

Ar ion laser IR diode laser, HeNe-Laser

27.05.2014 11:39 Laser Types in the AFM Lab

20 mW diode laser 532 nm

27.05.2014 11:39 Laser Pointers

laser pointers various wavelengths, up to 1000 mW

significant potential for eye injury!

27.05.2014 11:39 Quantifying Light: Power and Energy

• Watt: unit of radiant power ( = rate of flow of energy) • Joule: unit of radiant energy

• Example: laser beam of 3 Watts, emitted for ten seconds, generates a total energy during this time of 30 Joules

• emission of continuous wave different peak power, (cw) lasers: power P (Watts) equal energy • emission of pulsed lasers: energy Q (Joule) of each pulse

27.05.2014 11:39 Quantifying Light: Pulse Duration and Peak Power

average power

• example: Excimer laser

• typical pulse duration of tpulse = 20 ns

• pulse energy: Qpulse = 200 mJ

 peak power Ppeak = 10 MW

• for a repetition rate of 100 Hz: average power Paver = 20 W

• pulsed lasers can emit very high peak powers of several TW  highly hazardous • eye: averaging, looks like being low power  considerable hazard

27.05.2014 11:39 Quantifying Light: Irradiance

• interaction of laser light with material: irradiance

unit: W/cm2

unit: J/cm2

27.05.2014 11:39 Lamp vs. Laser

conventional lamp: extended source smallest patch of light that can be created by focusing is the geometric image of the source

laser: point source output can be focused by a to create a point image

 low divergence and therefore excellent focusability of laser radiation can cause high irradiances, even in large distances

27.05.2014 11:39 Irradiance

• lamp: 1 W at a distance of 1 m: 6 µW

• laser: 1 W at a distance of 1 m: 1 W

• lamp, 1 W, at a distance of 1 m diameter on retina: 100 µm irradiance: 0.1 W/cm2

• sun: diameter on retina: 0.35 mm irradiance: 6 – 100 W/cm2

• laser beam, 1 W diameter on retina :10 µm irradiance: > 1 MW/cm2

• hotplate: 3 W/cm2 Never stare into a laser beam!

27.05.2014 11:39 Never stare into a laser beam!

Virtually any laser is more dangerous than any other natural or artificial light source!

1 W laser ) 2 1 mW laser 20 kW Xe arclamp

welding arc

sun tungsten light filament hazard - blue

daylight fluorescent candle tube irradiance at the retina (W/m

image size at the retina

27.05.2014 11:39 Effects of Laser Radiation on Biological Tissue

• three different interaction processes: • photochemical reactions (creation of radicals, direct damage to DNA, …) • thermal interaction: heating  coagulation, vaporization • thermomechanical: • photoablation: spontaneous removal of tissue • disruption: ionization of tissue, extremely high temperatures and pressures

• effect depends upon the • irradiance of light • its wavelength • interaction time • penetration depth

27.05.2014 11:39 Hazards: Skin

• UV-C (280 nm – 100 nm): skin aging, skin cancer • UV-B (280 nm – 315 nm): erythema, enhances the hazard for cancer • UV-A (315 nm – 400 nm): hyperpigmentation • photosensitive reactions • skin burn • low-intensity IR irradiation: dilate blood capillaries, leading to inflammation

erythema skin burn

Beware: accumulating effects from long-time exposure!

27.05.2014 11:39 Hazards: Eye

laser beam damage can be • thermal burns • thermomechanical, acoustic shock • high-intensity short-pulse lasers: sudden vaporization of tissue which then causes a shock wave to spread, tearing other tissues in the eye • photochemical reactions • cause cloudiness in the eye tissue • result in a loss of light sensitivity

27.05.2014 11:39 Hazards: Eye

• UVC: absorption in the , photoconjunctivitis • UVB: (kindling of the cornea) • UVA: absorption in the lens, photochemical • VIS: high danger especially for the retina, photochemical resp. thermal effect advantage: eyelid-closing-reflex (< 0.25 s for healthy humans) • IRA: dangerous, radiation penetrates to the retina, but is not recognized  no eyelid-closing reflex, cataract • IRB: absorption mainly in the front part of the eyeball, thermal damage • IRC: absorption in the cornea, thermal damage

27.05.2014 11:39 Example: Exposures to the Eye

• exposure to a visible laser beam can be detected by • a bright color flash of the emitted wavelength and an afterimage of its complementary color • example: a green, 532 nm laser would produce a green flash followed by a red afterimage • when the retina is affected, there may be difficulty in detecting blue or green colors (secondary to cone damage), and pigmentation of the retina may be detected

• exposure to an invisible Q-switched Nd:YAG laser beam (1064 nm) • may initially go undetected because the beam is invisible, retina lacks pain sensory nerves • photoacoustic retinal damage may be associated with an audible “pop” at the time of exposure • visual disorientation due to retinal damage may not be apparent to the operator until considerable thermal damage has occurred

27.05.2014 11:39 Example

• work accident, both eyes were involved • 25 m distance, ruby laser (694 nm), pulse: 20 ns, 20 mJ (1 MW laser power) • personal perception: black spot, declining strength of sight • 5 days after the accident: blood bubble (diameter approx. 1.2 mm), strength of sight 5% • 3 years after the accident: scarf, strength of sight 5%

• 73% of all reported injuries are eye injuries, 35% of them associated with laser alignment; more than 68% of eye-related injuries result in permanent injury!

27.05.2014 11:39 Overview of Laser Hazards

27.05.2014 11:39 Remember: You only have 2 eyes!

27.05.2014 11:39 Classification

• class 1 • safe under all conditions of normal use • includes high-power lasers within an enclosure that prevents exposure

• class 1M • safe under normal conditions of operation • unsafe in combination with optical instruments (magnifying glass, microscope, etc. …)

27.05.2014 11:39 Classification

• class 2 • laser damages to the retina are prevented by the blink reflex (0.25 seconds exposure time) • only applies to visible light (400 nm – 700 nm) • limited to 1 mW • forced suppression of blink reflex can cause retina damages

• class 2M • same criteria as in class 2, but use of magnifying optics can cause eye damage

27.05.2014 11:39 Classification

• class 3R • „safe if handled carefully“, low risk • max 5 mW visible cw (limits differ for other wavelengths or fs-pulses) • may be hazardous under direct and specular reflection viewing conditions, normally not a diffuse reflection hazard

• class 3B • up to 500 mW visible cw (limits differ for other wavelengths or fs pulses) • must have key switch and safety interlock • may be hazardous under direct and specular reflection viewing conditions, normally not a diffuse reflection hazard

• class 4 • potentially dangerous laser • hazard to the eye or skin from the direct beam • diffuse reflections can be harmful • may pose fire hazard • must be equipped with key switch and safety interlock

27.05.2014 11:39 Classification, Safety Equipment

Laser-class properties comment

µW-range, limit depends on 1 safe for eyes and skin wavelength

µW-range/, limit depends on safe for skin, dangerous for the eye when 1M wavelength; total power < 0.5 W optical instruments are used

safe for skin, eye: safe via blink reflex or 2 1 mW; 0.25 s, 400-700 nm aversion

1 mW/pupil, safe for skin, dangerous for the eye when 2M 0.25 s, 400-700 nm optical instruments are used total power < 0.5 W 5x class 2; safe for skin, dangerous for the eye 3R 0.25 s, 400-700 nm safety glasses recommended 5x class 1; 100 s, when not visible might be dangerous for the skin, dangerous for 3B > 3R, max 0.5 W the eye safety glasses obligatory dangerous for skin and eye, fire hazard 4 > 3B personal safety equipment is necessary (glasses, screens)

27.05.2014 11:39 Laser beams are almost invisible, until they hit your eye!

27.05.2014 11:39 Usage of Lasers

• only trained users allowed to operate class 3 and class 4 lasers • laser safety goggles required for lasers higher or equally rated than class 3B (recommended for class 3R) • workplace must fulfill requirements necessary for lasers higher or equally rated class 3B

27.05.2014 11:39 Laser Area

• security of operation has to be verified before turning on the laser • every person in the laser area (entire optics lab!) during operation has to have a laser education or otherwise leave the area • laser operation has to be signaled at the entrance to the laser area (signs on) • access control for class 3B and for class 4 lasers required to prevent unauthorized personnel from entering the area

• turn off the laser signs if the laser is turned off

27.05.2014 11:39 Laser Signs

27.05.2014 11:39 Active Laser Safety

• act responsibly • use interlocks, remove keys when the laser is not operated • keep open beam paths to a minimum, using shieldings, guards, screens, curtains • use beam enclosures whenever possible • use beam blocks and traps, secure them from dropping

• use appropriate eye protection, i.e. safety glasses

• ensure that the maximum permissible exposure (MPE) is never exceeded

27.05.2014 11:39 Optical Density

• attenuation of light by a material • optical density

27.05.2014 11:39 Laser Safety Glasses

• depend on ThorLabs • wavelength • operational mode • minimum beam diameter

• declaration has to be written on the glasses • optical density (OD) for wavelength • sometimes L6@1024 R2@488

Never use goggles for the wrong laser!

27.05.2014 11:39 Declaration of Laser Goggles

• full protection glasses • attenuated to a level of class 1 lasers • withhold power for 10 seconds or 100 pulses • scale numbers L + optical density

• alignment filters • attenuation to a level of class 2 • only visible light • scale numbers R + optical density

27.05.2014 11:39 Declaration of Laser Goggles

27.05.2014 11:39 Good Practice

• don‘t put your body parts (particularly your eyes) in the beam! • never look directly into the laser beam, never into the beam path • work with the minimum power necessary • know where your laser is • take care of reflections and higher refraction orders • work in one horizontal plane • avoid a set-up in eye height (both for persons sitting and standing)

• close your eyes when your head is crossing the horizontal plane of the laser beam

27.05.2014 11:39 Good Practice

• block the beam while working on the beam path, never insert objects directly into the laser beam • don‘t work alone • work in bright ambient conditions • don‘t wear jewelry, rings or watches while working on a laser if they cannot be removed, cover with tape • use blackened/non reflecting components in the beam path • take extra care for • invisible laser • out-of-plane beam paths • inform your colleagues • do not direct any laser light towards windows or doors

• if in doubt: ask

27.05.2014 11:39 Other Hazards

• electrical shocks: high voltage, large currents

• mechanical (water / gas) • chemical (gas / dye) • temperature (fire) • explosion • secondary radiation (UV radiation from flash lamps for pumping, pump lasers)

27.05.2014 11:39 Other Hazards: Chemical

• laser media • organic dyes are major source of chemical hazards • mutagenic, carcinogenic, toxic, and/or highly reactive chemicals • gases from laser (e.g., Excimer laser) or interaction of laser with target (e.g., ozone) • Beryllium oxide (Ar+ laser)

• thermochemical decomposition of organic material: pyrolysis • PCCH • nitrosamines

• plastics (e.g. PMMA) • HCN • HCl

• laser generated air contaminants

27.05.2014 11:39 Other Hazards: Electrical

• most common non-beam hazard • high voltage from power supplies, capacitor banks

The optical beam can blind you, the high voltage can kill you!

27.05.2014 11:39 Other Hazards: Fire

• electrical circuits • improper beam enclosures • ignition of gases / fumes • flammable dyes

• use flame-resistant beam enclosures and check electrical circuits for safety to prevent injury

27.05.2014 11:39 Guidance for Laser-Lab Visitors

• no visitor is allowed unescorted access into a laser lab with a laser on without user approval • visitor guidelines • the escort or host will aid the visitor in selecting the proper eyewear to wear while visiting the laser-use area • all laser eyewear is labeled with wavelength coverage and OD • the visitor should always confirm that the correct eyewear has been selected and review the condition of the eyewear • host/escort guidelines • if at all possible, remove the hazard (turn off the laser) • prior to allowing entry, give a safety orientation • supply visitor with proper protective eyewear • at the conclusion of the lab visit, ask if the visitor has any questions or concerns • visitors should not left unescorted in the lab

27.05.2014 11:39 Laser Accidents

most common reasons for laser accidents 1. unanticipated eye exposure during alignment 2. misaligned optics and upwardly directed beams 3. available eye protection not used 4. equipment malfunctions 5. improper methods of handling high voltage 6. intentional exposure of unprotected personnel 7. operators unfamiliar with laser equipment 8. lack of protection for nonbeam hazards 9. improper restoration of equipment following service 10.failure to follow guidelines

27.05.2014 11:39 In Case of Emergency

• stay calm! • shut down laser • take care about treatment of injuries, visit hospital / ophthalmologist immediately (first 24 to 48 hours most critical), do not hesitate • inform supervisor / safety officer about • time of injury • kind of injury • how it happened • measurements taken

27.05.2014 11:39 Please sign the attendance list!

27.05.2014 11:39 Literature

• „Guide to Laser Safety“, Laservision GmbH • R. Henderson and K. Schulmeister, „Laser Safety“, Taylor&Francis (2004) • H. Welling, „Laser Safety“, in: Springer Materials, The Landolt-Börnstein Database, Springer-Verlag (2004) • L. Udovicic, „Damit nichts ins Auge geht … Schutz vor Laserstrahlung“, Bundesanstalt für Arbeitsschutz und Arbeitsmedizin (2005) • Lasersicherheitsbelehrung, Uni Duisburg Essen, Institut für Experimentelle Physik, AG Döbele • Lasersicherheits-Unterweisung, Holger Koch, EHF Oldenburg • K. Barat, Laser Safety in the Lab, SPIE Press (2013) • Laser Safety, Ralf Frese, NanoSyd

27.05.2014 11:39